Motor drive for sewing machines



June 3, 1924= H. MAIMIN MOTOR DRIVE FO R SEWING MACHINES Fi led Oct. 2

1923 2 Sheets-Sheet 1 TOR INV N 7 m (3 I B 7 13M, MM

A ATTORNEYS June 3. 1924. 1,496,478

H. MAIMIN MOTOR DRIVE FOR SEWING MACHINES Filed 061',- 26. 1923 2 Sheets5heet 2 INVEN OR 6 7 4 W MATTURNEYS hatente dune 3, i924 i MAN M 1 or new YORK, N. y Y.

MQTOR DRIVE NR SEWTNG MAGHINEE.

Application filed. fictober- 2% 1923. Serial No. 670,881.

To all whom'z't may concern:

of a belt shifter.

Be it known that l, l-lrMAN MAIMIN, a citizen of the United States, residing at New York city, in the county of New York, State of New York, have invented certain new and useful Improvements 'in Motor Drives for Sewing Machines; and I do hereby declare the following to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains to make and use the same.

This invention relates to a motor drive for sewing machines and more particularly to a variable speed drive.

One of the greatest difficulties attendant upon the operation of motor driven sewing machines is that of obtaining a nice speed regulation, quickly responsive to the touch of the operator, particularly at the very low speeds, where the machine must be under perfect control. Rheostats have, of course, been used for this purpose, but they are expensive and are a constant source of trouble. Because of this, many arrangements have been proposed for doing away with the rheostalt and driving the sewing machine at variab e speeds while running the motor continuously and at-constant speed. But none of these arrangements has proved entirely satisfactory, especially at the very low speeds. It is, therefore, the object of the present invention to provide improved means for regulating the speed of a sewing machine driven by a continuously running, constant speed motor. In particular, the object is to obtain better control at the very low speeds, and easy and quick transition from high to low speeds, and back' again.

I have attained this object by equipping the driving motor with a fast and a. loose pulley; the fast pulley being in the shape of a truncated cone with the small end adjacent the loose pulley, and of substantially the same diameter. The driving belt normally passes about the pulley on the sewing ma chine and this loose pulley, and is moved into and, if necessary, out of contact with the rapidly rotating cone pulley by means The length of the belt is designed to make a tig it driving fit when at maximum speed, .that is, when riding on the base of the cone, and it, therefore, makes only a loose contact with the small end of the cone. The resultant slippage coupled with the low ear ratio makes for a very low initial spec and one which is. well under the control of the operator. As the belt shifter moves the belt farther and farther along the face of the enlarging cone, the slippage becomes less and the gear ratio is increased, so that the speed can be rapidly increased until the maximum is reached, and the belt slips into a grooved seat at the base of the cone. Similarly, the belt can be moved toward the small end of the cone, and the speed quickly reduced.

It is a furtherobject of this invention to devise an improved gear shift mechanism controllable by the operator, and particularly designed for use in connection with the variable speed drive just described. This, together,with the other features of the invention will be more clearly understood when p more fully described in connection with the accompanying drawings, which disclose cer- Li I In Fig. I have illustrated, more or less diagrammatically, a conventional sewing machine I mounted upon a table 2, and pro-.

vided with the usual driven pulley 3, and hand wheel 4. The driving unit is situated immediately below the table and comprises a base 5, upon which is mounted a standard or pair of standards 6, which support the motor 7, and a treadle 8, by means of which the operator controls the speed of the machine,.as will be described. This driving unit is preferably made portable so that it can be set up under any given machine and readily positioned relative to the driving pulley of the machine.

Mounted upon the spindle 10 of'the motor are two pulleys, a fast cone pulley 11 and a loose ball-bearing pulley 12. The con-. struction of these pulleys and their relation to each other is shown most clearly in Fig. 4. The loose pulley is mounted adjacent the small end of the cone pulley and is of slightly less diameter than said small end, thus forming a small shoulder 13 at the place where the pulleys meet. This shoulder,

leys, as described above.

however, is on] slight and does not prevent the belt from being moved from the loose pulley onto the face of the cone pulley, but it does effectively prevent any unintended movement of the belt onto the cone pulley, and also serves to more effectively impart the initial driving movement to the belt. The loose pulley is slightly-grooved or concave. This also tends to hold the belt in position on the loose pulley when the sewing machine is still. The angle of the cone face of the fast pulley is such as to substantially align itself with the face of the cone pulley, with the exception of the "cry-small shoulder formed at the junction of these two pul- The base of the cone pulley is provided with an annular seat 14, havin When the belt is movedinto position on this seat for maximum speed, there is little tendency for it to move off. If there were, this oove 15 would counteract the tendency and hold the belt in position. The groove also has another function, that of prevent- .ing the metal clip, which joins the two ends of the belt, from striking against the pulley and making a noise. Thecone pulley is also rovided at its base with a'fiange 16, which makes it impomible for the belt to move off its seat on that side.

The driving unit is positioned so that the base 14 of the cone pulley 11 is in substantially the same plane as the pulley 3 on thesewing machine, so that when the sewing machine is being driven at maximum speed, the belt 17 'shall be running in a single plane. At this point, the belt is stretched to its maximum tautness.

In order to move the belt from the loose pulley to the fast pulley and hold it in any desired position upon the face of the cone, I have provided a novel belt shifting mechanism, which I shall now describe. (It is obvious, however, that other mechanisms might be employed for shifting the belt from one of the motor ulleys to the other.) Mounted upon one si e of themotor is a block 18, provided with two parallel bores 19, in which two rods 21 are slidahly mounted. Be ond the end of the block 18,

- these two r0 s are joined by means of a cross-head 22, which slides along a fixed rod 23, extending from the forward end of the block. The two rods 21 and the cross-head 22 constitute a frame, which acts as a belt shifter. The outer ends of the rod 21 are provided with ball-bearing rollers 24, dezigi'ned to contact with opposite sides of the e t.

This belt shifter with its belt contacting rollers is operated by means of the treadle 8, acting through a connection 25 and a bell crank lever 26 pivotally mounted at the outer end of the rod 23; one end of the bell crank lever being connected to the 0OI111C- a groove 15 in its middle.

meagre pressure on the treadle is relaxed. The two rollers 24 are so positioned that both of themn'ever contactwith the belt at the same time; and-when the belt is occupying either extreme position, that is when fully seated upon the loose pulley or upon seat. 14 of the cone pulley, there is a slight clearance between the belt and both pulleys.

In'accordance with the present invention, I have also provided novel means for applying a brake to the sewing machine when the belt has been moved into inoperative position. This brake is in the form of a bell crank lever 28, pivotally mounted on a standard 29 fixed upon the table 2 adjacent the hand wheel. The short arm of this bell crank lever carries a brake shoe 31, designed to contact with the hand wheel, when the sewing machine is to be stopped. The long arm of the lever extends through the table and makes contact with the upper rod 21 of the belt shifter. Thus, when the belt is upon the loose pulley and the parts occupy the position shown in Fig. 1, the brake is applied. As soon, however, as a pressure upon the treadle moves the belt shifter and the belt to the right, a spring 32 retracts the long arm of the lever'28 and releases the brake.

The ocperation of the drive may be briefly reviewe as follows: Starting from the position of rest shown in Fig. 1, the operator presses upon the treadle 8 and thus through the mechanism described moves the lower roller 24 into contact with the side of the belt. A slight further movement of the belt shifter pushes the belt into contact with the shoulder 13 on the rapidly rotating cone pulley.11. This contact imparts a slow creeping movement to the belt and causes the machine to be driven at a very low speed, the needle rising and falling very, very slowly. A slight further pressure on the treadle moves the belt beyond the shoulder and the speed is somewhat increased. The belt is, however, at this point under very little tension, and there is considerable slippage, so that the full speed of the cone pulley is by no means imparted to the belt. As the operator exerts further and further pressure upon the treadle, the belt rides further along the face of the enlarging cone, is drawn more and more taut, and is driven by a pulley of effectively increasing diameter. Thus'the speed at which the sewin machine is driven rapidly increases unti at the maximum, the belt slips'onto the seat 14. To drop backto slow speed for careful stitching, it is only necessary that the operator relax his pressure upon the treadle. Immediately the springs 27 move the belt shifter toward the loose pulley and the upper roller 24 dislodges the belt from the seat 11, and causes it to move down the face of the cone. The lower roller 24 prevents sudden movement of the belt to the left and makes it possible for the operator to slow down the machine at any rate he desires. The brake operates automatically as described above, to stop the machine as soon as the .belt has been moved out of contact, with the cone pulley, and to be released as soon as movement-toward the cone pulley is begun.

By means of the drive of this invention, I am enabled to obtain a practically perfect control of the sewing machine speed. The speed can be reduced to a point at which the needle is hardly moving. yet be under the operators control. This is very important and enables the operator to do difiicult and important stitching without the danger of running beyond the end of the seam. It is also possible by means of this drive to move quickly and effectively from very low to very high speed, and back again.

I claim:

1. The combination with a sewing machine having a driven pulley, of a cone driving pulley, a driving belt connecting the two pulleys, means for moving the belt longitudinally of the cone pulley to vary the speed of the sewing machine by varying the slippage of the belt, and means on the opposite side of the belt from the moving means cooperating therewith to hold the belt in any desired position upon the face of the cone pulley.

2. A variable speed motor drive for sewing machines comprising the combination of a motor, a fast cone pulley driven by the motor, a seat at the base of the come, a loose pulley adjacent the small end of the cone pulley and of substantially the same diameter. a driving belt designed to fit loosely about the loose pulley and tightly about the seat at the base of the cone pulley, and cooperating means acting on opposite sides of the belt for moving the belt from one pulley to the other and holding it at any desired position on the cone pulley to vary the slippage of the belt and the driving gear ratio.

'3. The combination with a sewing machine having a driven pulley, of a cone driving pulley, a loose pulley adjacent the small end of the cone pulley. and 'of substantially the same diameter as that end, a driving belt of less effective width than.

' the cone face of the driving pulley normally passing loosely about the loose pulley and the sewing machine pulley, and means under the control of the operator for moving'the belt longitudinally of the cone pulley and holding it in any desired position on the cone pulley to vary the slippage of the belt and hence the speed of the sewing machine 4. The combination with a sewing machine havlng a driven pulley, of a motor, a cone pulley driven by the motor, a loose pulley of a diameter substantially that of the small end of the cone pulley and mounted adjacent thereto, a driving belt normally passing about the sewing machine pulley and the loose pulley, a pair of belt shifting members, one designed to act on either side of the belt, movably supported adjacent the motor for moving the belt fromthe loose pulley to the cone pulley and back again, to vary the slippage of the belt and the speed of'the sewing machine, and means under the control of the operator ,for movin the .belt shifting members longitudina ly of the cone pulley and holding them in any desired position relative thereto.

5. A motor drive for sewing machines comprising the combination of a motor, a conical pulley driven by the motor, a loose pulley mounted adjacent the small end of the cone pulley, a frame slidably mounted adjacent the motor, rollers carried by the frame and designed to contact, one with one side of a driving belt passing around the pulleys. and one with the other, a treaclle, means actuated by the treadle for sliding the frame to .move the belt from the loose pulley across the face of the cone pulley, and automatic means for sliding the frame in the opposite direction to return the belt to'the loose pulley when the treadle ceases to act.

6. In a motor drive as claimed in claim 5, the loose pulley being provided with a groove and the base of the cone pulley with a grooved seat. neithen roller contacting with the belt when in either extreme position.

.7. In a motor drive for sewing machines, the combination of a motor, a fixed cone pulley onthe motor spindle, a loose pulley on the motor spindle adjacent the small end of the cone pulley and of slightly smaller diameter than said small end, a concave seat on the loose pulley, a grooved seat at the base of the cone pulley, both serving to hold a driving belt in either extreme position, and means for positively moving the belt across the face of the cone pull and holding-fit in any intermediate position.

In testimony whereof I affix my signature.

HYMAN MAIMIN. 

